Hot-plug storage drive

ABSTRACT

A drive assembly includes a carrier, a drive supported by the carrier, and an interface board. The tape drive includes a bus connector and a power connector. A plurality of cables are coupled to the bus connector and the power connector. The interface board includes an expander coupled to the cables and an external connector coupled to the expander. A storage array includes a backplane, a plurality of storage devices coupled to the backplane, a bus coupled to the storage devices, and at least one input/output connector coupled to the bus. Each storage device includes a carrier, a drive supported by the carrier, and an interface board. The drive includes a bus connector and a power connector. A plurality of cables are coupled to the bus connector and the power connector. The interface board includes an expander coupled to the cables and an external connector coupled to the expander.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates generally to storage devices used incomputer systems and, more particularly, to a hot-plug storage drive.

[0003] 2. Description of the Related Art

[0004] Most types of electronic and computing systems comprise manydifferent devices that electronically communicate with each other overone or more buses. Exemplary types of devices include, but are notlimited to, processors (e.g., microprocessors, digital signalprocessors, and micro-controllers), memory devices (e.g., hard diskdrives, floppy disk drives, and optical disk drives), and peripheraldevices (e.g., keyboards, monitors, mice). When electrically connectedto a bus, these types of devices, as well as others not listed, are allsometimes generically referred to as “bus devices.”

[0005] A bus, in the conceptually simplest form, is a collection ofwires over which the various electronic devices in a piece of electronicor computing equipment transmit information. However, any given bus maybe implemented in many different ways. A bus may be implemented so as totransmit only data, or only commands, or both data and commands, forinstance. But many more permutations are available based on otheroperating characteristics, such as bus width and bus speed. These twocharacteristics are exemplary only, and many other characteristics notlisted are considered in designing any particular bus implementation.Occasionally, an industry group will formalize a set of operatingcharacteristics into a “standard.” The standard will set flexibledefinitions for the standard that permit some variation in design butgenerally ensure compatibility for designs meeting the standard.

[0006] One such bus standard is the Small Computer System Interfacestandard (“SCSI”, pronounced “scuzzy”). There are actually manydifferent kinds of SCSI implementations, each defined by a differentSCSI standard. More particularly, at least the following varieties ofSCSI are currently implemented: SCSI-1, SCSI-2, Wide SCSI, Fast SCSI,Fast Wide SCSI, Ultra SCSI, SCSI-3, Ultra Wide SCSI, Ultra2 SCSI, FibreChannel, and Wide Ultra2 SCSI as well as some buses utilizing opticalinterconnections. The various SCSI standards are not necessarilycompatible with each other, although the basic SCSI standards (SCSI-1,SCSI-2, and SCSI-3) are basically functionally compatible.

[0007] Generally, SCSI began as a parallel interface standard used byApple Macintosh computers, PCs, and many UNIX systems for attachingperipheral devices to computers. The original intent was to develop aninterface providing faster data transmission rates (up to 80 megabytesper second) than the standard serial and parallel ports found oncomputers of the time. However, the SCSI standards proved to beenormously more useful than this original intent. One distinct advantageto the SCSI interface was that it permitted a user to attach manydevices to a single SCSI port in a daisy chain fashion. At the time,conventional serial and parallel ports generally were limited to onedevice per port.

[0008] The versatility inherent in the SCSI standards has allowed theinterface to be adapted to large scale computing environments, includingnetworks, both local area networks (“LANs”) and wide area networks(“WANs”). One large scale computing application is the implementation ofstorage arrays that use a plurality of storage devices, such as diskdrives or tape drives, that are grouped into arrays to providecentralized storage and backup capabilities. Some disk arrays areconfigured for bulk storage, while other configurations, such asRedundant Arrays of Inexpensive Disks (RAID) and Redundant Arrays ofInexpensive Tapes (RAIT), provide data redundancy to allow recovery inthe event of a storage device failure. The SCSI configuration allowsmultiple devices in the array to be simultaneously accessed, thusallowing increased transfer rates.

[0009] Typically, the setup of a SCSI system is complicated and requiresa high level of expertise on the part of the user. For example, a SCSIbus arrangement is typically arranged in a daisy chain fashion, whereone device interconnects with the adjacent devices on the bus. Both endsof the bus must be terminated (i.e., bus lines are pulled high) to allowfor proper transmission line characteristics and minimize reflections atthe ends of the bus. Improper termination, such as failure to terminateor terminating at places other than the ends of the bus, may reduce therobustness of the bus and even prevent its operation entirely.

[0010] To address the difficulties associated with configuring SCSIstorage arrays, computer system vendors typically provide externalstorage arrays with fixed configurations. Additional unused slots may beprovided for adding storage capacity. The bus configuration, however, isfixed. If a user has several servers and wishes to provide separatestorage arrays for each, separate external storage arrays must bepurchased and installed. Some storage arrays may be pre-configured toprovide two or more independent banks to allow separate arrays in acommon housing. However, these configurations are still static. Oneapplication might require a relatively small storage array while anothermight require a larger array. A user may either need to purchase eithera multi-array unit with a large capacity or two separate units withcapacity appropriate for the application. Either solution may not becost-effective.

[0011] One current trend in the storage device area is to providehot-plug capabilities for the devices. A hot-plug drive can be replacedwithout powering down the system. Currently, the SCSI standards define ahot-plug interface port standard and an accompanying single connectorattachment (SCA) connector for coupling hot-plug devices to common bus.If a drive fails, it may be removed and replaced. If a RAID data storagearrangement is used the data on the original drive may also bereconstructed. An SCA connector combines the bus, power, and SCSI IDconnectors into a single attachment. Mechanical features of the SCAconnector control the removal and application of power to the hot-plugdevice upon disengagement and engagement of the connector.

[0012] While SCA connectors have been used to standardize hot-plug harddisk drives, tape drives have not been provided with a similarstandardization. Current hot-plug tape drives have been developed withspecialized connectors that are compatible only with specific products.In one such implementation, the power connection is provided withhot-plug capability while the other connections remain unchanged. Suchdevices cannot be interconnected on a common bus with other hot-plugdevices due to signal integrity and bus citizenship problems resultingfrom the cable arrangement. For example, the additional cabling requiredto connect the standard connectors to the bus adds undesirablecapacitance and has the potential to disrupt the transmission linecharacteristics of the SCSI bus, rendering it unreliable or inoperative.

[0013] The present invention is directed to overcoming, or at leastreducing the effects of, one or more of the problems set forth above.

SUMMARY OF THE INVENTION

[0014] One aspect of the present invention is seen in a drive assemblyincluding a carrier, a drive supported by the carrier, and an interfaceboard. The tape drive includes a bus connector and a power connector. Aplurality of cables are coupled to the bus connector and the powerconnector. The interface board includes an expander coupled to thecables and an external connector coupled to the expander.

[0015] Another aspect of the present invention is seen in a storagearray including a backplane, a plurality of storage devices coupled tothe backplane, a bus coupled to the storage devices, and at least oneinput/output connector coupled to the bus. Each storage device includesa carrier, a drive supported by the carrier, and an interface board. Thedrive includes a bus connector and a power connector. A plurality ofcables are coupled to the bus connector and the power connector. Theinterface board includes an expander coupled to the cables and anexternal connector coupled to the expander.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The invention may be understood by reference to the followingdescription taken in conjunction with the accompanying drawings, inwhich like reference numerals identify like elements, and in which:

[0017]FIG. 1 is a simplified block diagram of a computer systemincluding a configurable storage array in accordance with one embodimentof the present invention;

[0018]FIGS. 2A and 2B are isometric views of alternative embodiments ofthe configurable storage array of FIG. 1;

[0019]FIG. 3 is a simplified block diagram illustrating the operation ofthe configurable storage array of FIG. 1;

[0020]FIG. 4 is a simplified top view of a hot-plug drive assembly foruse in the configurable storage array of FIG. 1 with the top portion ofthe carrier removed; and

[0021]FIG. 5 is a block diagram of the tape drive of FIG. 4.

[0022] While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and are herein described in detail. It shouldbe understood, however, that the description herein of specificembodiments is not intended to limit the invention to the particularforms disclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0023] Illustrative embodiments of the invention are described below. Inthe interest of clarity, not all features of an actual implementationare described in this specification. It will of course be appreciatedthat in the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

[0024] Turning now to the Figures, and first, to FIG. 1, a simplifiedblock diagram of a computer system 10 is provided. The computer system10 includes a plurality of servers 20, 30, 40 coupled to a configurablestorage array 50 by external cables 25, 35, 45, respectively. The numberof servers 20, 30, 40 depicted in FIG. 1 is chosen for illustrativepurposes only. Only one server 20 may be employed, or an even greaternumber of servers may be employed, depending on the specificimplementation and the connection capacity of the configurable storagearray 50. In the illustrated embodiment, the servers 20, 30, 40 areadapted to interface with the configurable storage array 50 inaccordance with a SCSI protocol, such as ANSI X3T10-1142. However, theapplication of the instant invention is not limited to a particular bustopology, and the teachings herein may be adapted to other current andfuture bus protocols. The configurable storage array 50 is adapted tosegment its internal bus and group its individual storage devices intosub-arrays depending on the particular manner in which the cables 25,35, 45 from the servers 20, 30, 40 are connected to the configurablestorage array 50, as discussed in greater detail below.

[0025] Turning now to FIGS. 2A and 2B, isometric views of variousembodiments of the configurable storage array 50 of FIG. 1 are provided.The configurable storage array 50 includes a plurality of storage units60, such as tape drives or disk drives, contained in a housing 65. Theparticular number of storage units 60 included in the configurablestorage array 50 may vary depending on the specific implementation. Inthe illustrated embodiment, the storage units 60 are hot-plug enabled,in that they may be removed and replaced without requiring that theconfigurable storage array 50 be powered down. A particular hot-plugtape drive assembly suitable for use in this application is described ingreater detail below in reference to FIGS. 4 and 5.

[0026] A plurality of external input/output (I/O) connectors 70-76 areprovided for connecting other devices, such as the servers 20, 30, 40 tothe configurable storage array 50. A power connector 80 is also providedfor supplying the configurable storage array 50. During a configurationcycle, the configurable storage array 50 determines which particular I/Oconnectors 70-76 have connections made thereto and groups the storageunits 60 into separate arrays based on such connections. Theconfiguration cycle may be performed when the configurable storage array50 is first powered up, or alternatively, the configuration cycle may betriggered in response to a user depressing a reconfigure switch 90 onthe configurable storage array 50.

[0027] In the embodiment depicted in FIG. 2A, the configurable storagearray 50 is adapted to automatically detect the desired arrayconfigurations based on the connections. Alternatively, in the secondembodiment illustrated in FIG. 2B, manual switches 100 are provided fordefining the array configurations. The manner in which the separatearrays are configured based on either the particular connections or thepositions of the switches 100 is described in greater detail below.

[0028] Referring now to FIG. 3 a simplified block diagram illustratingthe operation of the configurable storage array 50 is provided. Thestorage units 60 are coupled to a backplane 110, which is in turnconnected through a connector 120, to a control board 130. The backplane110 supports hot-plug operability. Mechanical features on theconnections from the storage devices 60 to the backplane 110 allow thebackplane 110 to determine if the storage device 60 is being inserted orremoved. The backplane 110 regulates power to the storage devices 60 asappropriate during the transitions. The particular construct andoperation of a hot-plug backplane, such as the backplane 110, arewell-known to those or ordinary skill in the art, and as such, specificdetails are not included herein for clarity and ease of illustration.

[0029] A segmentable bus 140 is provided for grouping the variousstorage units 60 into arrays. Expanders 150-156 are provided forinterfacing with the I/O connectors 70-76. One characteristic of a SCSIimplementation is that any connections, commonly referred to as stubs,extending from the main bus be no more that 0.1 m in length (i.e.,including internal wiring). The expanders 150-156 function to controlthe stub length and also perform a signal conditioning function on thesignals communicated through the I/O connectors 70-76. Expanders 160-165are provided for segmenting the bus 140 depending on the particulararray configurations. In the illustrated embodiment, the expanders150-156 are always enabled, and the expanders 160-165 are selectivelyenabled. Suitable devices for implementing the expanders 150-165 are anA 53C140 or an 53C180 ASIC sold by LSI Logic Corporation. Control logic170 interfaces with the various expanders, 160-165 for configuring thearrays. A suitable device for implementing the control logic 170 is acomplex programmable logic device (CPLD), such as a CY37064 offered byCypress Semiconductor Corporation. As will be appreciated by those ofordinary skill in the art, appropriate bus terminators (not shown) areprovided to comply with SCSI requirements that the bus be terminated atboth ends. For example, bus terminators (not shown) would be placedbetween the expanders 150-156 and the I/O connectors 70-76. Busterminators (not shown) would also be placed between the expanders150-156 and the storage devices 60, either on the control board 130 oron the backplane 110.

[0030] During a configuration cycle, the control logic 170 determineswhich of the I/O connectors 70-76 have cables 25, 35, 45 attachedthereto and groups the storage units 60 into arrays depending on theconnection arrangement. The control logic 170 may automatically sensethe arrangement, or the user may program the arrangement using theswitches 100 by activating the switches 100 corresponding to the I/Oconnectors 70-76 with connections made thereto. One technique forsensing the presence of a connection involves employing one of theunused ground lines on the bus. In the control board 130 the line istied to a voltage source (e.g., 5 volts). If no connection is made, thevoltage on the line will remain at the predetermined voltage level.However, if a connection is present, the voltage will be pulled toground. Using such a technique, the control logic 170 can readilydetermine which I/O connectors 70-76 have connections made thereto. Thecontrol logic 170 starts a new drive array at each connection point, asillustrated by the following examples. During the configuration cycle,the control logic 170 also configures the SCSI Ids of the storage units60 on the drive arrays. In the illustrated embodiment, the control logic170 sets the SCSI Id of the first storage device in each array to 0 andincrements for the additional storage devices 160 in the array.

[0031] If a connection is made at the I/O connector 70, and no otherconnections are made, the control logic configures all of the storageunits 60 on a common bus by enabling all of the expanders 160-165. Insuch a configuration, the segmentable bus 140 appears as a single buswith all of the storage devices 60 coupled thereto. If connections aremade to all of the I/O connectors 70-76, all of the expanders 160-165will be disabled, resulting in one storage device 60 being assigned perconnection. If the first connection were made to one of the I/Oconnectors 71-76 other than the first I/O connector 70, the expanders160-165 before the first connection would be disabled, leaving theassociated storage devices unused. In such a case the expanders 150-156associated with the unused storage devices 160 may be disabled by thecontrol logic 170 to prevent later connection to an improperlyconfigured array.

[0032] Differing size storage arrays may be constructed based on theparticular arrangement of connections to the I/O connectors 70-76.Consider the case illustrated in FIGS. 3A and 3B where a connection ismade to the first, fourth, and sixth I/O connectors 70, 73, 75. Theexpanders 160, 161 are enabled by the control logic 170 to define afirst isolated bus segment 180 in the bus 140 including the first threestorage devices 60. The segment is isolated by disabling the expander162. To define a second isolated bus segment 190 in the bus 140, thecontrol logic 170 enables the expander 163 and disables the expander164. Finally, the expander 165 is enabled to define a third isolated bussegment 200 in the bus 140.

[0033] After the configuration cycle is completed, i.e., after power upor pressing of the reconfigure switch 90, additional connections to thepreviously unused I/O connectors 70-76 may be made. These additionalconnections do not cause a reconfiguration of the arrays. Multiple cableattachment to the same logical isolated bus segment allows theconfigurable storage array 50 to support multiple-initiator transactionsas defined by the appropriate SCSI standards. The disabled expander160-165 located at the start of an isolated bus segment 190, 200 may bereferred to as being upstream of the connection to the I/O connector70-76, and the expanders 160-165 that are enabled to form the isolatedbus segments 180, 190, 200 may be referred to as being downstream of theconnection to the I/O connector 70-76.

[0034] Thus, by way of example and illustration, the expanders 150-156,160-165, control logic 170, and switches 100 (i.e., in the embodiment ofFIG. 2B) comprise means for determining an arrangement of connectorscoupled to input/output connectors of the configuring a storage arrayand means for grouping subsets of the storage devices onto isolated bussegments in the storage array based on the arrangement of connectors.

[0035] Turning now to FIG. 4, a simplified diagram of a hot-plug driveassembly 400 suitable for use as one of the storage devices 60 in theconfigurable storage array 50 of FIG. 1 in accordance with anotherembodiment of the present invention is provided. The hot-plug driveassembly 400 includes a carrier 410 adapted to support a drive 420. Inthe illustrated embodiment, the drive 420 is a tape drive, however, theinvention is not so limited, as other types of drives (e.g., hard diskdrive) may be used. For example, a standard non-hot-plug disk drive maybe provided with hot plug capability in accordance with the teachingsherein. In the case where the drive 420 is a tape drive, a number ofcommonly available industry standard tape drives, such as an SDX500C oran SDT 11000 offered by Sony, may be used. The drive 420 includes a busconnector 430, such as a typical 50 or 68 pin SCSI connector, a powerconnector 440, and an Id connector 450 (e.g., SCSI Id). These connectors430, 440, 450 are industry standard connectors commonly found onnon-hot-plug drives. The connectors are coupled by cables 460, 470, 480to an interface board 490 also supported by the carrier 410. An SCAconnector 500 is mounted to the interface board 490 for providing anindustry standard hot-plug interface. In the illustrated embodiment, theconnectors 430, 440, 450 are SCSI connectors, however, the invention isnot so limited as other bus topologies may be used. For example, otherbus topologies may not include a distinct Id connector 450. The specificconstruction and operation of the interface board 490 is described ingreater detail below.

[0036] Referring to FIG. 5, a block diagram of the hot-plug driveassembly 400 illustrating the operation of the interface board 490 isshown. The interface board 490 includes an expander 510 and a terminator520. The individual lines 530 from the cables 460, 470, 480 thatoriginate from the bus connector 430, power connector 440, and Idconnector 450 of the tape drive 420 are routed to the expander 510. Asuitable device for implementing the expander 510 is an A 53C140 or an53C180 ASIC sold by LSI Logic Corporation. The terminator 520 is coupledacross the lines 530 to comply with the SCSI bus rule that both ends ofa SCSI bus must be terminated. A suitable terminator 520 is a set ofUCC5638L IC's offered by Unitrode/Texas Instruments. The output of theexpander 510 is routed to the SCA connector 500.

[0037] The expander 510 minimizes the length of the stub seen at the SCAconnector 500 and cleans up the capacitance characteristics of thehot-plug drive assembly 400. The interface board 490 thereby improvessignal integrity and ensures proper bus citizenship while allowing theconversion from standard SCSI connections to an SCA connection. Thehot-plug drive assembly 400 may be inserted into any hot-plug SCAconnection along with other hot-plug devices, such as hard disk drives,cd-rom drives, etc.

[0038] The particular embodiments disclosed above are illustrative only,as the invention may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Furthermore, no limitations areintended to the details of construction or design herein shown, otherthan as described in the claims below. It is therefore evident that theparticular embodiments disclosed above may be altered or modified andall such variations are considered within the scope and spirit of theinvention. Accordingly, the protection sought herein is as set forth inthe claims below.

What is claimed:
 1. A drive assembly, comprising: a carrier; a drivesupported by the carrier, the drive including a bus connector and apower connector; a plurality of cables coupled to the bus connector andpower connector; an interface board, including: an expander coupled tothe cables; and an external connector coupled to the expander.
 2. Thedrive assembly of claim 1, wherein the drive includes an Id connector,and the plurality of cables includes a cable coupled to the Idconnector.
 3. The drive assembly of claim 1, wherein the interface boardfurther comprises a terminator coupled between the cables and theexpander.
 4. The drive assembly of claim 1, wherein the bus connectorcomprises at least one of a 50-pin and a 68-pin small computer systeminterface (SCSI) connector.
 5. The drive assembly of claim 1, whereinthe external connector comprises a single connector attachment (SCA)connector.
 6. The drive assembly of claim 1, wherein the drive comprisesone of a tape drive and a hard disk drive.
 7. A storage array,comprising: a backplane; a plurality of storage devices coupled to thebackplane, each storage device comprising: a carrier; a drive supportedby the carrier, the drive including a bus connector, a power connector,and an ID connector; a plurality of cables coupled to the bus connector,power connector, and ID connector; and an interface board, including: anexpander coupled to the cables; and an external connector coupled to theexpander. a bus coupled to the storage devices; and at least oneinput/output connector coupled to the bus.
 8. The storage array of claim7, wherein the drive includes an Id connector, and the plurality ofcables includes a cable coupled to the Id connector.
 9. The storagearray of claim 7, wherein the interface board further comprises aterminator coupled between the cables and the expander.
 10. The storagearray of claim 7, wherein the bus connector comprises at least one of a50-pin and a 68-pin small computer system interface (SCSI) connector.11. The storage array of claim 7, wherein the external connectorcomprises a single connector attachment (SCA) connector.
 12. The storagearray of claim 7, wherein the backplane comprises a hot-plug backplane.13. The storage array of claim 7, wherein the bus comprises a smallcomputer system interface (SCSI) bus.
 14. The storage array of claim 7,wherein the drive comprises one of a tape drive and a hard disk drive.